Armstrong's hydro-electric machine, 1845.
© Science Museum / Science & Society Picture Library
This machine was presented to the British physicist Michael Faraday by Sir William Armstrong (1810-1900). Armstrong's machine consisted of an insulated boiler filled with distilled water, which produces high presure steam that escapes through a row of jets after being partly condensed by pasing through pipes surrounded by cold water. The droplets strike a plate around which the steam has to pas before it escapes from the jets. This develops electricity in proportion to the increase of the presure of the steam; the jets become positively charged and the steam negatively. The machines were very powerful, but difficult to use. A 46-jet version at the London Polytechnic produced sparks two feet long. Made by H Watson, Newcastle-upon-Tyne.